As is known, this technology contemplates using a removable forming drum, winding a plurality of circumferential reinforcing filiform elements on the drum, covering the filiform elements by winding an adhesive coating tape thereon and pressing the adhesive belt against the filiform elements.
The adhesive belt, usually wound on reels, comprises a layer of carbon-fibre-based adhesive material and a protective or releasing strip arranged on only one side of the layer of adhesive material.
The winding and successive pressing of the adhesive belt, initially performed by hand and, later, using mechanized apparatuses, have been found to be extremely complex and delicate operations. In fact, incorrect or imprecise winding of the adhesive belt or an inadequate or uneven pressing of the adhesive belt cause the formation of blisters, contaminated areas and subsequent delamination and, in general, the formation of structural defects that result in inevitable rejection of the casing.
In current mechanized apparatuses, the winding and subsequent pressing are carried out using a deposit head supplied with the above-mentioned adhesive belt and moved by robotized arms. The application head is usually constituted by a belt unwinding device and a protective strip removal and recovery device.
In known applications, the protective strip is separated from the layer of adhesive material before the adhesive material is pressed against the forming drum and the reinforcing filiform elements.
In known heads, pressing is performed using a pressing roller that acts directly on the layer of adhesive material after the protective strip has been removed, and is rotatable about an axis orthogonal to the feed direction of the adhesive belt.
Although mechanized apparatuses of the above-described type are used, they are not entirely satisfactory, not only because they generate positioning errors and cause imprecise movement of the head along complex deposit paths, but above all because they are unable to avoid blistering and delamination on the casing being formed, in particular, as the geometrical/size characteristics of the casing change.
Better position control of the deposit head could be achieved by replacing the robotized arms with gantry movement structures, much more rigid and precise. However, these structures do not find practical application in forming plants using filament winding as they are extremely bulky, as well as being complex and expensive.
In addition, known mechanized apparatuses are not able to prevent contamination of the deposited adhesive material and to ensure uniform and homogeneous distribution of the adhesive material.
The foregoing is basically ascribable to the particular way the deposit head is implemented, the pressing roller of which soils itself, as it acts directly on the layer of adhesive material, often carrying part of the adhesive material with it, which it later releases when the chemical-physical characteristics of the material have changed.
Apart from this, during the depositing phase, the adhesive material is exposed to external contaminants on one hand, and lack of guidance on the other.
The lack of guidance of the adhesive material while being deposited inevitably results in positioning and compaction errors, which are even more pronounced for the leading and trailing portions of the adhesive belt.
Moreover, known mechanized apparatuses do not allow producing a uniform and homogeneous coating independently of the geometrical characteristics of the casing and, in particular, in the presence of protrusions or ribbing transversal to the belt's feed direction.
In fact, in these conditions, since it rotates about an axis orthogonal to the feed direction of the belt, the pressing roller is not able to compact the material in areas close to steps, with which it inevitably interferes and close to which blisters form or flaking takes place.
Lastly, the known solutions often make the application of adhesive materials difficult, as the latter, by their nature, tend to adhere more to the protective strip than to the reinforcing elements. In fact, in such cases, and especially in the phase of joining the belt's leading portion to the forming drum, it is often difficult to detach the adhesive material from the strip and make it adhere to the forming drum.